1. Field of the Invention
This invention relates to various image forming apparatuses such as a printer, a copying machine and a facsimile apparatus for forming images on sheets, and particularly to the detection of the position aberration of sheet conveyance and the sorts (or types) of the sheets therein.
2. Related Background Art
In an image forming apparatus, when conveying a sheet from a cassette, a tray or the like to an image forming portion, the sheet deviates in a main scanning direction (a direction perpendicular to the conveying direction of the sheet), and an image formed deviates relative to the sheet.
Also, in recent years, image formation on various recording mediums such as not only normal paper (opaque recording medium) but also overhead transparencies (OHT: transparent recording medium) and glossy paper (glossy recording medium) as sheets on which images are to be formed has been required.